Just recently my 97 explorer have been having this smell like burnt plastic and while inspecting the…

Just recently my 97 explorer have been having this smell like burnt plastic and while inspecting the hood i found this muddy substance on my tire could it be this?

what often happens is crud gets thrown on the exhaust system then burns and stinks it all up, check that, especially the catalytic converter

Is it something serious to be like that or do i have to take care of it right away

false